Without citing any exact numbers, Ballmer said Redmond is selling four times as many Windows Phone devices than at this time last year.

In addition, he said the Windows Phone Store now offers more than 120,000 apps, and that it will soon have "46 of the top 50 apps that people use."

Those aren't bad results for a product that launched only a month ago, and Ballmer's comments must surely have sounded encouraging to Microsoft shareholders, for whom the poor performance of the Windows Phone division has been a longstanding gripe.

Still, Ballmer has been talking up WP8 sales almost since the moment it launched. Until Microsoft releases actual sales figures – something it never did for Windows Phone 7 – it will be hard to gauge whether its new mobile OS truly has a chance of gaining a foothold against entrenched mega-competitors Android and iOS.

At Microsoft's annual Build developer conference in October, Ballmer acknowledged that Windows Phone has been "a small-volume player" – a nice way of saying that while Apple and Google have devoured ever-larger portions of the global smartphone market, Microsoft has been left squabbling for scraps with also-rans like Research in Motion.

In September of last year, a shame-faced Ballmer admitted to a group of financial analysts that first-year sales of Windows Phone 7 devices had been disappointing, but that Microsoft still had hopes of clawing its way into third place – hardly the most audacious goal.

Bearing that in mind, Ballmer's current claim of 300 per cent year-on-year sales growth doesn't sound nearly as impressive.

And what about that 120,000 app figure? Earlier this month, Research in Motion CEO Thoresten Heins told Reuters that he'd consider it a success if there were 100,000 apps in RIM's app store for its make-or-break BlackBerry 10 launch. By that standard, Windows Phone 8 would seem to be in fine shape.

The catch, however, is that BlackBerry 10 is an entirely new OS that breaks compatibility with previous versions of the BlackBerry platform. WP8, on the other hand, is backward compatible with most WP7 apps, and many of the apps currently in the Windows Phone Store are holdovers from the earlier OS.

In fact, Microsoft reported that its store had crossed the 100,000 app threshold in June, five months after reaching the 50,000 mark. Based on Ballmer's current figure, it only added 20,000 more apps in the next five months, indicating that its growth is actually slowing.

Don't expect anything but positive spin from Ballmer, though. The Microsoft CEO has said the company is "all-in" on WP8, and as closely aligned as Redmond's Phone strategy is with its Windows 8 strategy, to hint at anything less than success now risks upsetting the whole apple cart.

If Windows Phone 8 isn't actually meeting Microsoft's expectations, however, it wouldn't be entirely unexpected. Earlier this month, HP printer and PC veep Dan Tindall told The Reg that HP had passed on producing a device for the WP8 launch because it felt the opportunity was, as Tindall tactfully put it, "smaller than explosive in the first few quarters." ®